Experimental assessment of commercial one-coat renders for buildings façades

This paper presents an experimental study on a selection of commercial one-coat dry renders by means of laboratory tests, focused to analyze early age shrinkage strain and microcracking, on Kraai tests on fresh mixtures and hardened render specimens. Thermogravimetry (TG) weight loss measures were accomplished on hardened renders to ascertain their basic composition, and to correlate the water/cement ratio prescribed by the manufacturer, with the water just added to the mortar on site. It was obtained that the basic composition of modern dry renders is quite similar to that used to design ancient waterproofing mortars. A two-stage Arrhenius-type relationship was obtained from TG weight loss tests, universal for all the tested one-coat tested and in close correspondence with the enthalpy involved in the lime hydration/dehydration cycle. The long-term storage capacity of CO2 from the atmosphere, in the lime contained in one-coat renders of the exterior façades of buildings, is shown.